1. Field of the Invention
The present invention relates to a gas handling device assembly, and more particularly to a gas supplying apparatus which is used in a chemical vapor deposition (CVD) apparatus for a semiconductor manufacturing process.
2. Description of the Related Art
A construction of a gas supplying apparatus used for a CVD process is required to supply a process gas in a stable condition so that semiconductor devices having a uniform quality are manufactured. Additionally, the gas supplying apparatus must have a construction of which maintenance can be performed in a short time so that a down time of a manufacturing facility due to the maintenance is minimized. Further, the gas supplying apparatus is preferred to have a compact size so that a manufacturing apparatus is miniaturized.
FIGS. 1A, 1B, 1C and 2 show a conventional gas supplying apparatus 10. The gas supplying apparatus 10 has a gas inlet 11 into which a process gas is supplied and a gas outlet 12 from which the process gas is discharged. Between the gas inlet 11 and the gas outlet 12, there are provided a stop valve 13, a mass flow controlling device 14, a stop valve 15, a filter 16 and a stop valve 17, in that order. These devices are arranged on a base plate, and connected via tubings 19 using connectors 18. Each of the stop valves are mounted on the base plate 35.
The gas supplying apparatus 10 also has a purge system 30 and a gas discarding system 31. The purge system is provided for introducing a purge gas N.sub.2 into the gas supplying apparatus 10. The purge system 30 is provided with a pressure controlling valve 32 and a stop valve 33. The gas discarding system 31 is provided for discarding the process gas remaining in the gas supplying system 10. The gas discarding system 31 is provided with a stop valve 34.
In a case in which trichlorosilan (SiHcl.sub.3) is used as the process gas, tape heaters (not shown in the figure) are applied to each of the stop valves 13, 15 and 17 and the tubings 19 connecting therebetween so that these devices are heated to prevent the process gas from liquidizing.
The above-mentioned gas supplying apparatus 10 has the following problems.
1) The maintenance is not easy and takes a long time.
It is supposed, for example, that the mass flow controlling device 14 is replaced with a new one. First, the connectors of the mass flow controlling device 14 are disconnected. If the mass flow controlling device 14 is removed from the gas supplying apparatus 10 in this state, sealing surfaces of an inlet port and an outlet port of the mass flow controlling device 14 may be scratched or damaged because there is no clearance between the sealing surface of the inlet and outlet ports of the mass flow controlling device 14 and a sealing end of the respective tube 19 which was connected to the mass flow controlling device 14.
In order to prevent the sealing surface of the mass flow controlling device 14 from being scratched or damaged, other devices such as stop valves 13, 15, 17 and 33 and the pressure controlling valves 32 must be loosened to provide clearances between the inlet and outlet port of the mass flow controlling device 14 and the respective tubings 19.
The operation for making clearances are required for replacing other devices, and thus the maintenance of the gas supplying apparatus 10 may take much labor and a long time.
2) The size of the gas supplying apparatus 10 becomes large.
Each of the component devices of the gas supplying apparatus 10, such as the stop valves 13, 15, 17, 33 and 34, the mass flow controlling valve 14 and the pressure controlling valve 32 has an inlet port and an outlet port on opposite side-faces thereof. The tube 19 and connectors 18 must be provided between the component devices. Accordingly, a relatively long distance is needed between the component devices, which distance is indicated, for example, by distance a between the mass flow controlling device 14 and the stop valve 15 shown in FIG. 2. Therefore, a length b of the gas supplying apparatus becomes long as shown in FIG. 1B.
3) A constant supply of the process gas may not be achieved.
Heating using the tape heater may generates an uneven temperature distribution along the tubings and the component devices. When a gas, which tends to be easily liquidized, is used as the process gas, the process gas may be liquidized at a portion where sufficient heating is not applied. The liquidized gas may block a flow of the process gas, and thus a constant supply of the process gas cannot be achieved.